Worth playing, but overrated
It's not a real Assassin's Creed game. It's good as a pirate simulator (not an accurate/realistic one, but a very fun one), and it's amazing as an open-world seafaring game!
However we get no new present-day protagonist, instead a weird meta (and mute/brainless) first-person protagonist thing, and the pirate protagonist, Edward, spends almost the whole game only after cash, and being a fool. The assassins, the creed, and all that made Assassin's Creed different from other action-adventure games are barely there. The combat went kind of backwards as we can use a lot less weapons now.
Also, things can get so repetitive. For many hours the game is addictive, but after plundering over 50 ships, which I had to in order to upgrade stuff, I just want to skip those parts.